Google’s search engine is technically complex. There are hundreds (some say thousands) of different factors taken into account so that the search engine can figure out what should go where.
Google’s first job is to ‘crawl’ the web with ‘spiders.’ These are little-automated programs or bots that scour the ‘net for any and all new information. The spiders will take notes on your website, from the titles you use to the text on each page to learn more about who you are, what you do, and who might be interested in finding you.
Google’s next job is to figure out how to best match and display the information in its database when someone types in a search query. So the information in its database needs to be categorised correctly, rearranged, and displayed in less than a second after someone expects it.